Motor startup and braking simulation in Simulink - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding Motor Startup Dynamics

Which physical quantity primarily determines the initial acceleration of a motor during startup in a Simulink model?

A The length of the motor shaft

B The motor's moment of inertia

C The ambient temperature

D The motor's steady-state speed

💡 Hint

Think about what resists changes in rotational speed.

The moment of inertia represents how much the motor resists changes in its rotational speed, thus affecting acceleration during startup.

❓ Predict Output

intermediate

Simulink Model Output for Motor Speed

Given a Simulink motor startup model with a step input voltage applied at time zero, what is the expected shape of the motor speed output over time?

A A speed that oscillates indefinitely

B A constant speed from the start

C A curve starting at zero and gradually rising to a steady speed

D A speed that decreases over time

💡 Hint

Consider how motors respond to sudden voltage application.

The motor speed starts at zero and increases gradually due to inertia until it reaches a steady-state speed.

❓ data_output

advanced

Analyzing Braking Torque Data

In a motor braking simulation, which data output correctly represents the braking torque over time if the brake is applied suddenly at 5 seconds?

Simulink

time = [0, 2, 4, 5, 5.1, 6, 8, 10];
braking_torque = [0, 0, 0, 0, -50, -50, -50, -50];

A [0, 0, 0, 0, -50, -50, -50, -50]

B [0, 0, 0, 0, 50, 50, 50, 50]

C [-50, -50, -50, -50, 0, 0, 0, 0]

D [0, 0, 0, 0, 0, 0, 0, 0]

💡 Hint

Braking torque is negative when applied to slow the motor.

The braking torque is zero before 5 seconds and then suddenly becomes negative to apply braking force.

❓ visualization

advanced

Interpreting Motor Speed and Torque Graph

Which graph correctly shows motor speed decreasing while braking torque is applied after 5 seconds?

A Speed curve rises continuously; torque zero throughout

B Speed curve constant; torque constant positive throughout

C Speed curve falls from start; torque positive then zero

D Speed curve rises to steady state then falls after 5s; torque is zero then negative after 5s

💡 Hint

Braking torque slows the motor, so speed should decrease after brake application.

The motor speed increases initially, then decreases after braking torque is applied at 5 seconds, which is negative torque.

🚀 Application

expert

Optimizing Motor Startup and Braking Simulation Parameters

You want to simulate a motor startup and braking scenario in Simulink. Which parameter adjustment will most effectively reduce the motor's stopping time after braking is applied?

A Increase the braking torque magnitude

B Increase the motor's moment of inertia

C Decrease the input voltage during startup

D Increase the motor shaft length

💡 Hint

Think about what force directly slows the motor down faster.

Increasing braking torque applies a stronger force to slow the motor, reducing stopping time.